1. Field of the Invention
The present invention relates to an outer race member of a roller type one-way clutch that is employed for an automatic transmission, etc., wherein engagement members are interposed between an inner race member and the outer race member.
2. Related Background Art
A roller type one-way clutch classified as one type of one-way clutch has a construction in which rollers defined as engagement members are pressed against and thus engaged with a cam surface formed on an inner peripheral surface of an outer race member or on an outer peripheral surface of an inner race member, thereby locking rotation in one direction.
FIG. 5 is a partially cut-away front view of this roller type one-way clutch in the prior art. A roller type one-way clutch 30 is constructed of an inner race 32 as a solid shaft member and an outer race 33 into which the inner race 32 is fitted. The outer race member, i.e., the outer race 33, is formed on its outer peripheral surface, with pawls 38 for engaging with an unillustrated opposite member.
Block bearings 37, rollers 36 and springs 35 for biasing the rollers 36 in an engaging direction, are disposed between the inner race 32 and the outer race 33. The outer race 33 has a cam surface on its inner peripheral surface, and the rollers 36 engage with this cam surface, thereby locking the rotation.
The springs 35 and the rollers 36 constitute a torque transmission mechanism, and the rollers 36 are held by a cage 34. The block bearings 37 effect positioning of the cage 34 with respect to the outer race 33.
The roller type one-way clutch is subject to potential fatigue failure originating from a groove for disposing the block bearing due to repetitive free/lock operations. Therefore, a thickness of the outer race in a radial direction becomes larger for ensuring a sufficient strength.
On the other hand, a decrease in weight is required of the roller type one-way clutch as a whole. It is therefore desired that the two requirements in terms of the strength and the decrease in weight be met simultaneously.
A roller type one-way clutch as described above is disclosed in Japanese Patent Application Laid-Open No. 11-051091. This document teaches that a weight of the whole one-way clutch is reduced by integrally forming the cage by use of plastic.
As disclosed in Japanese Patent Application Laid-Open No. 11-051091, if the cage is formed of plastic, this can reduce the weight. However, there still remains a problem in terms of the strength. Further, because the cage is not particularly heavy in the first place, the one-way-clutch is still heavy because of a heavy weight of the outer race member, etc.